That's all I have to say about that.
Okay, not really. I guess I should explain why it's crap.
~ Firstly, almost all of the dialogue is just exposition. Didn't you know that passengers on cruise ships always have casual chats about the fact that there's an opening in the hull around the propellors? Of course they do.
~ And related to that, there's no character building, just a few glances at character when something dramatic is happening (ie something more dramatic than the general ship-sinking activity). The audience has very little reason to care about the main characters because we don't really know them.
~ Really stupid things happen that just wouldn't happen. For example at one point the main characters are traipsing along corridors looking for an exit and when they stop to talk, the mum realises the son has wandered off. Honestly, people. When you're desperately trying to escape a sinking ship and you've already almost lost your son once, you just don't let him wander off. And a terrified child in said sinking ship doesn't just wander off. It was such a stupid moment. Then, we see the adults trying to free the child from behing a locked gate as the water's rising over their heads and all I could think was why doens't he just go back the way he came, he wandered in there on his own after all? The kid disappears (shock! panic! NOOO!) and then, lo-and-behold!, he's found his way back the way he came through an easily opened door. My goodness. It was awful. And there were too many other "oh that SOO wouldn't happen!" moments.
~ Something that was quite hilarious - all the main characters had some kind of awfully convenient background that helped them solve their dilemma. Every second scene had someone saying "I used to be a firefighter, I can...." or "I'm an architect, I know how this was engineered". After a while the group of friends I was watching with were joining in with similar sentiments like "I used to be a man-of-steel, I can just break us out of the hull". My contribution was "It's okay, I was an actor in the original Poseidon movie, I know exactly how to get out".
Anyway, enough rambling about an awful film.